Bucket for turbines.



No. 885,098. PATENTED APR.'2I, 1908.

;o. P. 'STEINMETZ. BUCKET FOR TURBINES.

- APPLICATION FILED NOV. 21, 1905.

2 SHEETS-SHEET 1.

. 2/ I v Q I t v Witnsses: y Inventor:

W y, a Charles P. Steinmetz bB UM- No. 885,098. PATENTED-APR. 21,1908. I 0, P. STBINMETZ. I

BUCKET FOR TURBINBS.

' APPLICATION FILED NOW 21, I906.

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Inventor: Charles P. Steinmetz b:I

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To all whom it may concern.

" UNITED STATES PATENT onnrcn.

CHARLES P. STEINMETZ, OF SCHENECTADY, NEW YORK, ASSIGN OR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK. v

BUCKET FOR TURBINESJ Specification of Letters Patent.

Patented April 21, 1908.

Application filed November 21, 1905. Serial No. 288,389.

Be it known that I, CHARLES 1 -8mm METZ, a citizen of the United States, residin at Schenectady, county of Schenectady, an State of New York, have inventedcertain new and useful Improvements in Buckets for Elastic-Fluid Turbines, of which the followingris a specification. V c his invention relates to buckets or blades for elastic fluid turbines, and its object isrto provide a bucket so sha ed that it will vary .the centrifugal force 'of't e elastic fluid flowing through it, preferably in such a mannerthat the increase of centrifugal acceleration.

and retardation are constant. In the ordinary type ofbuckets, the, elastic fluid enters tan ent again. "In the entering'tangent the flu1 moves 1n straight'lines so that no centrifu alforce'is exerted. Onentering the force suddenly rises from zero to a circu a1. portion ofthe bucket the centrifiulgal 1te value which remains constant until the fluid leaves the curved portion for the quitting tangent, when the centrifugal force suddenly becomeszero a ain.' There is thus a sudden I shock im arte to the fluidcolumn at each end oft e circularportion' of the bucket;

causing compression on enteringrthe bucket and expansion on quitting it, givin rise to 'oscillatlons which result in a-loss o ener y and cause wasteful eddy currents in t e steam.

. By my invention I provide for an increase of the centrifugal force from zero or afinitesmall value at the beginning of the-curved portion of the bucket .to a given maximum at the middle of said curved portion, and a decrease of centrifugal forcefrom the middle 'versa.

of the bucket to t-hebeginning of the nit-1 ting tangent, whereit fa ls to zero or a ite small va us again. I prefer to provide for a regularand gradual increase and decrease of the centrifugal force. But this is not absolutely essential, as the variation may be at first rapid and then more gradual, or vice In the following description, however, I shall assume that the variation is to be uniform and regular.

The formula for centrifugal force (F =MV shows that the force varies inversely as the radius, if the mass and velocity remain constant.

In the stream of steam flowing through a turbine bucket the mas" and the velocity do not alter appreciably. therefore,the curve of the bucket is such that the radius of curvature shortens from infinity or a small finite value to a given minimum and then lengthens to infinit or a small finite valuenagain, the centr' .ugal force of the steam Will increase and decrease accordingly.

The ratio of variation may be different; for instance, the successive radii may all vary by-a*"constant uantity, or each may d ffer from the prece 'ing one by a constant fraction thereof.

,The result of constructing a bucket on these lines is that the steam leaves it in a jet of constant velocity. moving in a uniform direction, which rendersv it of maximum efficiency when directed againstthe buckets of another wheel. This result is not possible if shocks are imparted to the steam b the sudden application andwithdrawal o centrifugal force in its passage through the bucket, whereby it leaves the bucket in a scattered jlet, varying invelocity and in direction. he invention is, therefore, of especial value in turbines which extract the velocity energy from the steam in several successive wheels.

' In the accompanying drawing, Figure 1 is a diagram of a curve composed of a lurality of arcs of equal length described y radii which .form a harmonic progression of a given initial radius; Fig. 2.is another diagram in which each radius-isseVen-eighths ofthe preceding one; Fig. 3 shows the outline of several turbine buckets conforming to these curves; and Figs. 4 and 5 are slightly modified forms of buckets having somewhat thicker ed es. 1

It will e noticed at a glance that the curves are spirals. In Fig. 1, the radius X is laid off at. some given length, and with this the .arc 1 is described, of a given length y. .The next. arc 2is described with a radius the are 3 with aradius and so on, the

lengths of all the arcsbeing the same, and the successive radii being a harmonic-progression;that is, the. reciprocals of an arithmetical progression varymg by one, the

initial radius being unity. The spiral is we point 4 one-eighth of the length of the line 45 or 4-7. With the line 6-7 as aradius, I

the arc bis described, of the same length as the are a. The distance, 8 9 is seveneighths of the line 6,-7 or 65 9, the dis'-' tance 10 -11 is-seven-eighths of the line- 8.9 or 8-11, and so uni -Each offthe arcs c, d, e, etc., is-equalf to a. The curved spiral line is made up of the arcs-a,'b, 0,

etc; A' bodyiofgiv'en massmovingalon either of these curves at uniform speedwi be subjected to a regularly increasing centrife' ugal'force which atgany given point is.pro-' portional to the length oftheradius'at that J point-j j Forinstance, the'radius ,12'13' .18 one and three-fourths-ti'mesi the radius.

' 14+15 (whichitis very.'.;nearly)-'then the centrifugal; force"of zthegbody as it moves through the arc 12 is orie and three-fourths times that which itfhad along. the are Fig. 3 shows the-'iu'tiliz'ationiof .a"'spiral curve in layin out a turbine bucket. a i the drawin that portionof the curve shown in heavy b ack hasbeen-'selected-; but it is evident that the length of the portion, takenwill depend upon. the width of the bucket,

which in the drawing isrepresented .by'the space between the parallel lines, 16.-17. 25 andalso the direction of the steam flow-' ing from the nozzles,.and make angles of 24 with the line 16. The quitting angle, thatvv is, that between the line 17 and the is 30. with the lines 1819'at the curves being duplicates.

bucket. It is apparent that the spiral bucket has a somewhat longer curve/but the slight increase surface v'fr'ictionwill be more than offset by the elimination of shock .and eddies. q 4

The back wall 24 of the'steam passa e may beof any .suitableconfiguration; pre erably a curve parallel with the front of the passage,

' as shown. The height of the bucket may be.

such as. the size of e wheel requires, and it may or may not provide for an expansion of the steam, as preferred. With these matters my invention has-nothing to do, being dihe lines 18 indicate the'walls' ofthe no z zle" ines 19,. The sides of the bucket coincide oints' 20'-21 'From the point 20 to the point 22,. onthe,"

center line of the bucket, thelcurve isof "de,- creasing radius, while from the point 22, ;td the point 21 it is just the reverse "the necessarythickness of stock rected solel to the curve of thew'orkin surface'ofthe ucket, as hereinb'efore set. orth'.

f The back wall of the bucket is a straight line up tothe point opposite the beginnmg of the front wall. The front wall, as before stated, starts with zero curvature, and the curvature gradually increases to a maximum at the center line of the bucket, and then (19? creases again to zero at the exit.. 'The low curvature at the ends of the bucketsresults in an'extremel'y thin knife edge, and where this is impracticable for mechanical'or other reasons I employ the arran ements shown in "Fig. 4. In this figure t e bucket curve starts, not at zero curvature but at a given small radius as at. 26, which decreases toward the center line of the. bucket. The dotted line 27 indicates the circular or standard bucket; 'It will be noticed that with this arran ement the ed es of the buckets may be t ickened to t e desired degree.

Thls bucket shape gives a less sharp edge but it impresses av certain small centrifugal ac-.

celeration to'the fluid at the point of en trance, which, however," is very small compared tothe standard buck'et and may be" disre arded.

i In, ig, 5 is shown a bucket'with the front I -wall shaped to give the correct acceleration fIQlIl ZQIQiJO the given maximum at the entrance and" a, decreasing acceleration from maximum to zero at theexit with theback wall thickened 'toward'the'edges to give the.

or mechanical reasons. I

In the drawings the arcs of successive radii are shown of equal-len th since this is the preferred arrangement ut 'itis within the scopeof my invention'to make them of different lengths. The point of maximum curva-' ture as showninthe drawings coincides with the center line of the bucket structure but for-,difierent conditions I'maylocate it on either side thereof.

Ihaveshown what I consider to be the best methods of forming the bucket surfaces but they are'to be understood as being only illustrative, since the buckets may be formed in'fa variety of ways so long as the generic ,I featureof theinvention is preserved. The dotted semi-circle 23 inside the? curveof the bucket showsthe line of the ordinary" l :"jThe buckets shown are intended primarily for steam turbines but it is obvious that they maybe used with material advantage in turbines using other kinds of elastic fluid. The nozzles or other fluiddischarging devices may be of any suitable form or con struction and expanding or nonexpanding in character. i I What I claim as new, and desire to secure by Letters Patent of. the United States, is,- 1. An elastic fluid turbine buckethavmg Ia cui'vedsurface developed by radii which vary in a harmonic rogression. 2. An elastic flui turbine bucket havin a curved surface developed by a radius whic means for gradually varying the centrifuga shortens up to the middle point of the bucket and then lengthens.

3. A U-shaped elastic fluid turbine bucket having a surface composed of two spiral 5 curves. Y

4. An elastic fluid turbine bucket having a surface composed of two spiral curves, one the reverse of theother.

5. An elastic fluid turbine bucket'havin force of' the steam-flowing through it to obviate shock.

6. An elastic fluid turbine bucket" having means for first graduallyincreasing and then gradually decreasing the centrifugal force of the steam shock. v

7. An elastic fluid turbine bucket having means for first uniformly increasing and "then flowing through it to obviate uniformly decreasing the centrifugal force of the steam flowing through it.

8. An elastic fluid turbine bucket having two straight end portions at an angle with each other,- and an,intermediate' curved ortion which is tangent to the strai ht portlons at 3 from said ends to its midd e each end and is described b decreasing radii point. 1

9. An elastic fluid turbine bucket having two straight end portions at an angle with each other, and an intermediate curved portion which is tangent to the straight portions at each "end and is described by constantly decreasing radii from said ends to its middle point.

10. An elastic fluid turbine bucket having two straight end portions at an angle with each other, and an intermediate curved portion which is tangent to the straight portlons at each end and is described from said ends to its middle point by radii which decrease in a harmonic progression.

11. In an elastic fluid bucket, the combination of a device which discharges motive 'force and com ression of the fluid entering from an initia to a maximum value, and gradually decreases the centrifugal force and compression of the dischargin fluid from the maximum to a redetermine value. 7

In witness w ereof, I have hereunto set my hand this 20th day of November, 1905.

CHARLES P. s'rEINMETz.

Witnesses:

BENJAMIN B. HULL, HELEN ORFORD. 

